Two Baylor hospitals are the top U.S. centers for a clinical trial that potentially could yield a method to tame uncontrolled high blood pressure—without medication.
Medtronic is testing a minimally invasive procedure called renal denervation in what it calls the Symplicity trial.
One of the body’s primary methods for controlling blood pressure involves the sympathetic nervous system. The system includes the major organs that are responsible for regulating blood pressure: the brain, the heart, the kidney and the blood vessels themselves.
One key player in long-term blood pressure regulation is the kidney. Renal nerves communicate information between the brain and kidneys. In people with hypertension, the renal nerves often are hyperactive, which raises blood pressure and contributes to heart, kidney and blood vessel damage.
Renal denervation involves inserting a tube in the groin and placing the device in the artery leading to the kidney. The device produces heat by radio frequency to disrupt nerve communication between the brain and kidneys. Multiple treatments are performed in each artery to disrupt the hyperactive nerves.
The trial, now in its third phase, includes more than 500 patients at up to 90 U.S. hospitals. The two Baylor sites—The Heart Hospital Baylor Plano and Baylor Heart and Vascular Hospital Dallas—are No. 1 and 2 respectively among the third-phase hospitals in number of enrolled patients.
David Brown, MD, principal investigator at the Plano facility, said the study is a randomized, controlled double-blinded trial, meaning neither the patients nor the investigators know which patients received the procedure. He said half of the patients receive a “sham treatment” that does not disrupt the nerves. After six months, those that did not receive the procedure have the ability to “cross-over,” or receive the treatment.
Brown called hypertension is a “silent killer” because it does not have symptoms. He said about 1 billion worldwide have high blood pressure, and that is expected to rise to 1.6 billion in a decade. Of those, he said about one-third is untreated, one-third is treated and controlled, and one-third is treated by poorly controlled by medication. The clinical trial is aimed at the last group.
Brown said physicians try to keep patients below a systolic blood pressure reading of 140. He said patients double their risk of dying of cardiovascular disease for every 20-millimeter increase in mercury. On the other hand, every 2 millimeter decrease lowers the risk of stroke by 10 percent and cardiovascular disease by 7 percent.
Brown said the trial participation requirements were that patients have average systolic readings of at least 160 and taking maximum doses of at least three hypertension medications. He said about one-third of the trial enrollees have systolic readings of more than 180. He said the Baylor sites will continue to enroll participants for at least another year.
James Choi, MD, the principal investigator at the Dallas facility, said about 5 percent of U.S. adults initially would have qualified for the study. However, once physicians put those patients on maximum medication dosages, about half get their blood pressure under control.
Choi said Baylor is attracting enrollees from as far away as Amarillo and Tulsa, Okla.
The first two phases of the trial have shown promising results, with average reductions of about 30 millimeters that have been maintained over three years.
Choi used a cell-phone analogy in describing how the procedure seeks to turn the sympathetic nervous system “from a 4G network into a 1G network. You can’t obliterate central body functions completely.”
Brown said, if successful, renal denervation could represent “a paradigm shift in treating hypertension. It could be a one-time treatment to replace all those expensive medicines.”
Choi said Medtronic, which has more than a dozen competitors seeking to do similar procedures, likely would fund secondary studies to expand the criteria for wider use if the current trial succeeds.
“How about all those 35 year olds (with hypertension) who were destined to take pills for the rest of their lives? This is exciting stuff,” he said.
Steve Jacob is editor of D Healthcare Daily and author of Health Care in 2020: Where Uncertain Reform, Bad Habits, Too Few Doctors and Skyrocketing Costs Are Taking Us. He can be reached at [email protected]